Steve Irwin, the hugely popular Australian television personality and conservationist known as the "Crocodile Hunter," was killed Monday by a stingray while filming off the Great Barrier Reef. He was 44.

Irwin was at Batt Reef, off the remote coast of northeastern Queensland state, shooting a segment for a series called "Ocean's Deadliest" when he swam too close to one of the animals, which have a poisonous bard on their tails, his friend and colleague John Stainton said.

"He came on top of the stingray and the stingray's barb went up and into his chest and put a hole into his heart," said Stainton, who was on board Irwin's boat at the time.

Crew members aboard the boat, Croc One, called emergency services in the nearest city, Cairns, and administered CPR as they rushed the boat to nearby Low Isle to meet a rescue helicopter. Medical staff pronounced Irwin dead when they arrived a short time later, Stainton said.

Irwin was famous for his enthusiasm for wildlife and his catchword "Crikey!" in his television program "Crocodile Hunter." First broadcast in Australia in 1992, the program was picked up by the Discovery network, catapulting Irwin to international celebrity.